Citrix Provisioning Services version 6.0 is a great improvement over the previous version! Why? Simply because management of the vDisks has become so much better than it was before. But if you want to stay happy after a server crash, you need to keep one little thing in mind?. Please read on.
Before version 6.0 you needed to make a copy of your vDisk, import it into the vDisk Store, put it in Private Mode and link it to a test device if you wanted to make a change to an image. By then, you had spent an hour waiting for several GB's to finish copying. If you were lucky enough (or just very good?) to do your change correctly the first time, you could then make the image read-only again and proceed with testing. If you screwed up your image, well, you just had to make a new copy and drink some more coffee? right? Citrix introduced vDisk versioning in the version 6.0 release of Provisioning Services, which makes updating and testing vDisk images a lot easier. Citrix basically changed the definition of a vDisk, from a single VHD file to a collection of a base image VHD file together with a chain of referenced VHD differencing disks. The documentation shows it like this:
The same task as described above for the previous versions now comes down to: make a new differencing disk and set the version access to Maintenance, boot your test device that is linked to the Maintenance type of your vDisk and make your changes. Did something go wrong in the change procedure? No worries, just throw away your differencing disk and start over again. With vDisk versioning this will only take you minutes and no more storage than needed for the delta of the change. It really is that fast and that simple?.
However?. When disaster strikes and you need to restore your vDisks from any kind of back-up to your Provisioning Services environment, you cannot just copy your vDisks into the Store location and do an import as you could do with the old versions of Provisioning Services. You may be able to import your base VHD vDisk, but if there is a chain of differencing disks you will not be able to import them if you forgot to create an export of the vDisk. Previously only the copy of the VHD file was enough for a backup, but now you need this export because it describes the relation between the base image and the differencing VHDs. Provisioning Services 6.0 creates this export in the form of a XML file that is placed in the vDisk Store. You create the export with a right click on the vDisk.
In the dialog that follows you can create the export, but keep in mind that it will only describe the Base and Test chain, not a Maintenance disk you may have in the chain.
Conclusion: Make regular exports of your vDisks (and include them in your backup) and you will be even happier with this version of Provisioning Services!
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